[NiHaoMike]

Are you using classical PWM or some sort of Delta Sigma? The latter would require a FPGA but those are quite cheap! A Spartan 6 LX16 board goes for $20 nowadays and would be plenty to implement inverter logic with. Delta Sigma, if implemented correctly, boosts efficiency especially with IGBTs. From my understanding, it uses less transitions during particularly low/high parts of the cycle. (I tried to get similar results by programming a dsPIC to period skip during extreme duty cycles but it's just not the same.)

You can really do some cool tricks in power electronics using custom logic. One that I'm working on is a bidirectional DC/DC converter - easy to implement in theory but good luck trying to find an off the shelf ASIC that supports that kind of control!